The present invention relates to a method for producing a separating nozzle element comprising a separating body and terminal plates for the separation of gaseous or vaporous mixtures. Gaseous or vaporous mixtures are understood to mean, in particular, isotope mixtures, such as .sup.235 UF.sub.6 and .sup.238 UF.sub.6, which due to their chemical characteristics, make special demands on the material of the separating nozzle elements.
In a separating nozzle process, the gas pressure leading to the minimum specific energy consumption is inversely proportional to the characteristic dimensions of the separating structure, as disclosed in Chemie Ing. Technik, Volume 39 (1967) at page 4. Since the specific costs for compressors, pipelines, valves and control devices required for the implementation of the process decrease considerably with increasing gas pressure, it is desirable to make the separating nozzle structure as small as possible. the presently employed or desired inlet pressures between 0.5 and 1.5 bar correspond to a narrowest width between 10 and 3 microns for the deflector slit in the separating structure.
It is known to produce separating nozzles having particularly small characteristic dimensions and which are comprised of a separating body and terminal plates. The separating body is here penetrated by separating structures which define separating chambers and gas conduits, while the terminal plates include channels for the intake and discharge of the gas streams See German Pat. No. 2,933,570 and corresponding U.S. Pat. No. 4,351,653.
At the points where the separating structures are delimited by the terminal plates, there results by nature a deceleration of the gas stream decisive for the separation, resulting in a loss of separating output. This loss is the greater the smaller the ratio of thicknesss of separating body to narrowest width of the separator slit. This ratio is referred to herein as the "separating body aspect ratio". To keep separating output losses resulting from deceleration at the terminal plates as low as possible, separating body aspect ratios between 100 and 200 must be attained. Thus, with the narrowest width of 3 microns for the separating slit, the separating body should have a thickness between 300 and 600 microns.
Separating bodies having a narrowest width of a few microns for the separating slits can be produced with the required accuracy according to present-day knowledge by providing a plate of or a layer of a material whose characteristics can be changed by high-energy radiation. Negative molds containing the separating structure are formed from the material whose characteristics can be changed by high-energy radiation. The negative molds are formed by partial irradiation of the material, that is, by irradiating only selected portions of the material, followed by partial removal of material, to thereby utilize the different material properties generated by the irradiation. Depending on the nature of the material whose characteristics can be changed by irradiation, the material which is removed can be either the selected portions which have been irradiated, or can be the non-irradiated portions. In either case, the negative molds are then filled with a structure material which is compatible with the gaseous or vaporous mixture to be separated to thereby form the separating structures. The remaining material of the negative molds then is removed. In order to realize particularly high separating body aspect ratios, the process may be performed in stages, if required, as disclosed in German Pat. No. 2,933,570 and U.S. Pat. No. 4,351,653.
The separating nozzle elements produced in this manner, due to their extremely small characteristic dimensions and the relatively high gas pressure connected therewith, permit considerable savings in the above-mentioned system components. The costs for producing the separating nozzle elements themselves, however, are still relatively high compared to the costs of the other system components. Therefore, they may take up a considerable fraction of the total investment costs for an industrial separating nozzle system which lie in the order of magnitude of several billions of Deutsche Marks (approximately at least about 1 billion U.S. dollars). This problem of costs for the manufacture of separating nozzle elements is all the more difficult because the previously most successful use of the above-mentioned manufacturing principle utilizes so-called synchroton radiation, which makes the production dependent on the availability of an expensive electron accelerator.